Drilling fluid composition and process



United Stat 3,087,923 Patented Apr. 30, 1963 ice 3,087,923 DRILLINGFLUID COMPOSITION AND PROCESS Ellis Gray King and Carl Adolphson,Bellingham, Wash,

assignors to Puget Sound Pulp & Timber (30., Bellingham, Wash., acorporation of Delaware No Drawing. Original application May 25, 1959,Ser. No. 815,294, new Patent No. 2,935,473, dated May 3, I960. Dividedand this application Apr. 1, 1963, See. No. 19,167

25 Claims. (Cl. 260-124) Our invention and discovery relates toimprovements in drilling fluids resulting from a novel combination ofclays and specially treated suifonated lignin-containing material.

More particularly our invention relates to an improved drilling fluid ormud composition or combination, and to a process for use thereof. Thismod combination may be formulated to function as water base drillingmods, for example and not limitation as fresh water mud, as lime basemud, as gypsum mud, as calcium chloride mud, as salt contaminated or seawater mods, and in emulsion mud systems. Furthermore, the mudcombination is usable over the entire pH range of drilling mud fiuidsused in the field. A particularly novel form of our mud system is thecombination with gypsum which is especially useful in drilling oil wellswhen anhydrite is encountered. Heretofore, a well recognized fact isthat sulfonated lignincontaining additives such as those derived fromspent sullite liquor are effective as thinners in lime base mods butsuch are not useful as thinners in fresh water mods.

Moreover, our improved mud combination is characterized by stability tohigh temperature and by effectiveness in resisting the deterioratingeffects of comtarninants encountered in drilling. Such effectiveness isparticularly advantageous in drilling deep wells where high temperatureand pressure exists.

Our invention and discovery herein relates primarily and fundamentallyto the providing of a novel combination of drilling mud clay andsulfonated lignin-containing material whereby there results drillingmods of newly found properties. It would be ditllcult to find a moresensitive test of the increased effectiveness of the components of ourinvention than those required to meet the properties of said drillingmods.

The improved effectiveness of the components of the sulfonatedlignin-containing material provided by our invention and discoveryrenders them suitable as a drilling mud additive, or as the base fromwhich an improved drilling mud can be formed, which mud is characterizedby having greatly improved properties.

This application is a divisional application based on our copendingapplication Serial No. 815,294, filed May 25, 1959, entitled DrillingFluid Composition and Process, now U.S. Patent No. 2,935,473, which inturn is a continuation-in-part of our copending application Serial No.433,794, filed June 1, 1954, entitled Process of Improving theEffectiveness of the Components of Spent Sulfite Liquor and the ProductsThereof; our copencliug application Serial No. 539,542, filed Octoberll), 1955, entitled Process of Improving the Effectiveness of theComponents of Spent Snlfite Liquor and the Products Thereof, now U.S.Patent No. 2,935,504; our copending application Serial No. 769,185,filed October 23, 1958, entitled A Process for Providing an ImprovedDrilling Fluid and the Product Thereof; our copending application SerialNo. 789,775, filed January 29, 1959, entitled A Process for Providing anImproved Drilling Mud of Clay and a Metal Lignosulfonate and the ProductThereof; and our copending application received in U.S. Pat. OiliceMarch 19, 1959, Serial No. 806,974, entitled An Improved Gypsum BaseDrilling Fluid and the Products Thereof. The methods of treatingsulfonated lignin-cor1- taining material through oxidation and saltformation in improving the dispersive properties of said sulfonatedlignin-containing material and the combination of said additive productswith clay and water in forming drilling muds are completely disclosed insaid copending applications. Furthermore the unexpected resistance ofsuch muds to the contaminants encountered in oil well drilling was alsoset forth.

The outstanding properties of suitable magnitude which characterize ausable and practical drilling mud comprise the following: (1) initialgel strength; (2) viscosity; (3) 10-minute gel strength; and (4) waterloss, which relates to the sealing oil of the wall of the drilling holeby building up a filter cake of mud on the wall, thus preventing loss ofwater from the mud. Thus, it is manifest that the drilling mud, with itsexacting requirements of various properties for the mod, is a mostimportant, involved, and complex feature of oil and gas well drilling.

Universally, a drilling mud (having about the consistency of lubricatingoil) is used in a circulating system with rotary Well drillingmechanism, and is forced by pump ing down the hollow drill stem throughthe bit which it lubricates and cools, then back to the surface to asettling pit. Thus it washes out the cuttings which have been made fromthe hole, and the cuttings are carried outside the drill stem to thesurface where the coarse particles are caused to be removed and the mudagain used in a continuous circulating process. To prevent the loss ofthe mud in porous strata, the mud must be of a character to seal offsuch strata and the mud, by its hydrostatic pressure, must prevent theescape of gas, that is prevent the well from blowing out. To provide theproper hydrostatic pressure, the specific gravity of the mud may beincreased by adding heavier material than clay, such as barytes. On theother hand the drilling fluid must have the proper viscosity, that is,be thick enough to carry out the cuttings, but thin enough to be pumpedand to allow the course particles to settle out in the surface mud pitsso that the mud may be re-used.

Our invention and discovery is characterized by making it possible togreatly improve the effectiveness of the components of said sulfonatedlignin-containing material with very simple and inexpensive equipment.The simplicity of the treatment of our invention and discovery is one ofits outstanding features.

One important property of drilling mud is that in case of temporarystoppage of work, the mud should gel" sulficiently to prevent settlingof the suspended cuttings, which settled cuttings would seize the drillstem and prevent re-starting or its withdrawal from the well. From thisit is manifest that the viscosity of the fluid is highly important.Likewise, the property to gel or to set like gelatin is important whenthe agitation incident to drilling ceases. Thus, the mud will hold insuspension the cuttings and at the same time become fluid when agitationis resumed. This is called the thixotropic property of the fluid, or itsgel strength. Most clays have this property but not all. Such propertymay be increased by adding the clay called bentonite and similarsubstances. As the drilling proceeds through different strata, theviscosity and gel strength may be affected by the character of thestrata, by the loss by absorption of water in the porous strata or inthe inflow of water and other fluids, by temperature changes, or bychemically active substances which may enter the drilling fluid as thedrilling proceeds. Accordingly, viscosity, gel and water loss are verycarefully watched and corrected from time to time during the drilling.There are instruments provided for testing such properties at the mouthof the well.

In the early history of well drilling, water was added to thin the mud,but this had the objectionable result of re ducing the specific gravityof the drilling fluid and thereby decreased its hydrostatic pressureproperty, and also decreased its ability to suspend the cuttings and thebarytes which had been added to give weight. Also, to overcome theeffect of addition of chemicals from the strata through which the wellproceeded, i.e., the effect from so-called contaminants, other chemicalswere added to offset the deleterious effects.

In fact, the literature relating to drilling muds is so extensive andcomprehensive and has extended over such a long period of time that itis very apparent that important difficulties, mechanical, chemical andeconomical, are involved in the controlling, conditioning, and obtainingof the proper type of drilling mud. It is one of the fundamental objectsand purposes of this invention and discovery to provide a drilling fluidcontaining an inexpensive and highly effective mud additive to overcomethe problems that have existed for so long in this field. Let it alwaysbe kept in mind that the value of the drilling mud depends on how muchit will contribute to speed, efficiency, and safety in oil and gas Welldrilling. Our invention and discovery provides a combination of clay andtreated sulfonated lignin-containing material, which combination ischaracterized by its economy as well as its very special effectiveness,not only for one of the two primary recognized types of drilling muds,i.e., lime base and fresh water muds, but for the special effectivenessof both of said types of mud.

An important and fundamental object of our invention is to provide agypsum base mud characterized by a low gel rate rather than the usualobjectionable high gel rate which is usually accompanied by high flatgels. Such muds accomplish the maintaining of suitable gels so thatcuttings fall out in the mud pit Without the necessity of watering backto thin the mud. In this way, the need for costly water loss reducingagents such as carbOxy-methylcellulose is substantially lessened, if noteliminated, and the amount of expensive weighting agents required fordeep wells is decreased.

RELATIVE CONTAMINANTS In the drilling of deep wells such as oil and gasby the employment of a mud laden drilling fluid as in the rotary systemof drilling, strata of a contaminating character may be encountered inlarge masses which often supply calcium sulfate to the drilling mudthisis very disadvantageous and alters or destroys required properties ofthe mud, Such calcium sulfate may be, among other forms, in the form ofgypsum (calcium. sulfate with water of crystallization) and anhydrite(calcium sulfate without Water of crystallization). The literaturestates (Rogers, Composition and Properties of Oil Well Drilling Fluids,page 377):

The first small additions of calcium sulfate increase the viscosity andgel strength of the mud fluid greatly but do not increase the fluid lossappreciably. This peak portion of the viscosity curve is reached at anaddition of 33.3 ppm. calcium per gram of bentonite. As theconcentration of calcium sulfate increases, the viscosity decreases andthe fluid loss increases sharply."

As the concentration of the calcium sulfate increases, the viscositydecreases and the fluid loss increases sharplyobviously this featureevidences unpredictable character of contaminants upon the components ofthe drilling muds as respects the important properties which mustcharacterize the mud. The different properties of the mud are affecteddifferently. Rogers further states (said text, page 378): Qunfortunately, the addition of the soluble sodium sulfate results in alarge increase in viscosity and gel strength. This effect is of such amagnitude that the method cannot be used in the field to overcome theadverse effects of the anhydrite. It can, however, be demonstrated inthe laboratory."

The discovery and invention herein disclosed shows how thisobjectionable feature of sodium sulfate has been overcome, and to thisextent the invention and discovery of applicants is contrary to therecognized literature in this field.

Other contaminating strata are salt beds and the cement employed in theconstruction of the well. Also let it be noted that the contaminants maybe a combination of the contaminants disclosed herein.

It is the primary and fundamental purpose of our invention and discoveryto provide a drilling mud system or combination of clay and sulfonatcdlignin containing material which will operate in controlling thecolloidal and physical properties and for maintaining the requiredproperties of a water-clay drilling mud which may be subject tocontaminants, so that the mud combination will function in a moreeffective and more economical manner than heretofore. Thus, an importantpart of our invention is the rendering more effective the properties ofthe sulfonated lignin containing materials and herein resides protectionagainst contamination.

This part of our invention relating to the sulfonated lignin containingmaterials is commonly referred to as the drilling mud additive. Ourpurpose is to provide such an additive of a character which willfunction as a control product for the colloidal and physical propertiesand for maintaining the required properties of the water clay drillingmud which may become subject to contaminants in the drilling operationand to provide such an additive when combined with the mud that willfunction in a more efficient and more economical manner than has beenaccomplished heretofore.

The part of our invention and discovery which relates to a furtherimprovement in lessening water loss of gypsum contaminated muds involvesthe addition of sodium sulfate or equivalents as hereinafter listed tothe combination of clayey material and the additive lignosulfonateproduct of our invention and discovery, in the proportion of 1% to ofsaid sodium sulfate or equivalents by weight of the additivelignosulfonate product, said addition being made in proportionsdetermined by a pilot test of a drilling mud which is contaminated withcalcium sulfate. The additive product of our invention in and of itselfmay not produce the extremely low water losses desired in some muds. Theaddition of the sodium sulfate and equivalents as hereinafter listedwill further reduce the water loss to the desired level and at the sametime said additive product prevents the large rise in viscosity and gelfactors which occurs when sodium sulfate alone is added to an aqueoussuspension of clayey material. Thus in the presence of the additivelignosulfonate product, the ordinary adverse action of the sodiumsulfate is depressed.

Sometimes the formations are of thick dolomitic lime or other rocksections which do not contribute good mud making materials. In suchcases it is necessary to control or maintain the mud by addition dailyof bentonite to develop the desired low fluid loss, and the pH of themud is maintained on the alkaline side to promote hydration anddispersion of the drilled shales. The alkaline pH promotes higherviscosities in the bentonite clays, and, therefore, thinners are addedand those with alkaline properties such as the sodium tannate type arepreferred.

These thinners, because of the presence of alkaline sodium salt, aid inthe formation of sodium clays from the dispersed shales and alsoincrease the degree of dispersion of the clays and shales and hencereduce the fluid loss to strata surrounding the hole. In general, the pHor alkalinity of such muds is maintained at about 9.0 or 10.0. At timesthe pH of the mud rises or is carried to the range of 10.5 to 11.5 inwhich the clays and bentonite present manifest appreciably higherviscosity. The treatment of these muds is with sodium hydroxide andquebracho (sodium tannate), and they are referred to as red muds. In allof these cases, the principal contaminants are salt, cement, gypsum oranhydrite, sand, and other inert mineral matter.

When the mud viscosity becomes too high, it may be more economical toconvert to the so-called lime base mud rather than to dilute with waterinvolving the necessary addition of weighting material. At other times,the contamination becomes so bad that the chemicals are not effectiveand it is found necessary to convert to the lime base mud. Thisconversion involves the addition of an excess of lime and caustictogether with a thinner such as quebracho or, preferably,lignosulfonates. This type of high pH mud with an excess of lime ishereinafter referred to as a lime base mud as contrasted to all of theother water clay muds previously discussed, which for convenience willbe hereinafter termed fresh water muds.

OBJECTS In general, quebracho, as a thinner, has been used in all typesof muds, both fresh water and lime base, but quebracho is an expensivecommodity. To date, the lignosulfonates have been useful only in limebase muds where they are well known to be relatively inexpensive, butuntil now, i.e., until the present invention, it has not been possibleto use the lignosulfonatcs in the lower pH (less than 12, i.e., freshwater) muds not containing an excess of lime, inasmuch as they have noappreciable thinning action on such muds. One of the primary objects ofthis invention is to provide a drilling fluid composition containing anadditive comprising a soluble sulfonatcd lignin-containing materialwhich is highly effective, not only as lime base muds, but also as freshwater type muds.

A primary and fundamental object is to provide a drilling fiuiddispersing agent derived from spent wood pulping liquor solids in thesimplest and most economical manner with relatively inexpensiveequipment, and in a continuous manner to produce from these said liquorsolids a soluble additive for drilling mud systems or combinations whichis effective in reducing the viscosity and gels of both fresh Water mudsand the so-called lime base muds, even in the presence of substantialquantities of natural contaminants such as anhydrite, sodium chlorideand sodium sulphate.

Another objective is to provide by a sequence of steps a drilling fluidadditive derived from spent wood pulping liquors which are preferablyinitially purified and fractionated and then modified to obtain asoluble additive for making the mud combination of our invention whichis characterized by the fact that molecules of each fraction are of aparticular and different molecular average size and especially usefulfor dispersing agents in general and additives for drilling muds inparticular.

Another primary object of our invention is to provide a drilling fluidadditive produced by preparing and fractionating chlorinatedlignosulfonates to provide said chlorolignosulfonates in fractions ofspecific molecular Weigh to adapt the same to a particular purpose. Itis particularly the object of this invention to provide drilling fluidcompositions containing soluble spent sulfite liquor additives that arenot only especially lower in cost, but are highly effective and usefulin essentially all types of water clay and oil-in-water emulsiondrilling muds.

Still another obiect of this invention is to provide a drilling mudadditive which is suited for use with saline or sea water when freshwater is not readily available. Mud prepared with sea water has specialutility in offshore drilling where fresh water must be transported tothe drilling site and fresh water muds must be protected from sea watercontamination. We have found that the additive of our invention issurprisingly effective as a thinner not only for gypsum base muds, butalso for saline muds made up originally with sea water as the aqueouscomponent together with commercial drilling mud clays.

A further object of the present invention is to provide a drilling fluidadditive comprising sulfonated lignin-containing material which has beentreated at high temperatures, e.g., about C.2l0 C., to improve itsproperties.

DEFINING STARTING MATERIALS Spent lignin liquors from the pulping ofwood provide an inexpensive source of the raw material for our processand product, the said liquors being available in large quantity as wasteproducts of the pulping processes. One of our aims is to conserve thiswaste material.

The preferred raw material is derived from the pulping of wood by thecalcium bisulfite process for the manufacture of pulp. In this operationa substantial portion (20% to 70% usually about 55%) of the wood isconverted to water soluble products which at the end of the cookingprocess are separated from the pulp in water solution. This solution,because of the washings, is very dilute, ranging approximately from 5%to 20% solids. This solution can be used as such in our process or itcan be concentrated in any one of several well known ways to a moreconcentrated solution which is more readily and economically handled,particularly because of the smaller volume of liquid involved, Theconcentrated solution can range from 30% to 70%, but handles better inthe range of 40% to 50% total solids in solution. This concentrationsolution contains lignosulfonates as salts {for example calcium,magnesium, sodium, or ammonium salts, depending on which of these areemployed in the digesting process), carbohydrates, and other complexorganic compounds derived from wood, as well as inorganic compoundseither present in the wood or derived from the reaction. Furthermore,digesting of wood by iron or aluminum bisulfite will give a spentsulfite liquor component which may be our raw material and which willobviate the necessity of a base exchange reaction to form the iron oraluminum salts. The concentrated solution may be used in our inventionand it is very desirable to do so. However, the spent sulfite liquor canbe further refined before or after processing according to ourinvention. For example, the spent sulfite liquor can be essentiallyfreed of carbohydrate material by any one of a number of procedures,preferably by fermentation. Also, said carbohydrates may be removed bydialysis, by separation with organic solvents or organic bases, or byprecipitation as basic lignosulfonates, for example, with lime or bysalting out with salts such as calcuim chloride or sodium chloride. Inaddition, the lignosulfonates, as well as being freed as far as possibleof extraneous materials, may be fractioned as to molecular weightcomponents.

Any of these above described products are basically derived from spentsulfite liquor solids, and are sulfonated lignin-containing materialsand the degree of refining to which they are subjected either before orafter the steps of our invention will depend on the quality of productdesired and the economics invloved. That is, refining to some extentwill improve the properties of the final processed product, but thedegree of improvement will not always be economically justifiable. Infact, it is an essential and outstanding feature of our invention anddiscovery that we can use concentrated spent sulfite liquor as such, andthrough a series of simple steps involving equipment which is relativelyinexpensive, can produce products which are equivalent in properties,for instance,

for use as drilling mud additives and dispersants, to the purifiedlignosulfonates.

In general, any type of wood or lignocellulosic material, the sameincluding straw, cornstalks, bagasse and the like, which can be resolvedto pulp With the separation of the lignin-containing material, may beused as a source for providing lignosulfonate in following ourinvention. Furthermore, changes in the final properties of the productare influenced by the conditions of the pulping process, but in generalgood results are obtained using the commercial spent sulfite liquor fromeither paper grade quality pulp or dissolving grade quality pulp.

In addition to the spent sulfite liquor derived from the acid bisulfitepulping of wood, liquors containing soluble lignin are also availablefrom the netural and alkaline pulping of wood or other lignoeellulosicmaterial. Such lignin-containing materials may be coverted to sulfonatedlignin-containing materials usable as raw materials for the process ofour invention, for instance by treatment with sulfites at elevatedtemperatures, chlorination and heating with sodium sulfite or by othermethods known to those skilled in the art, subject only to getting asoluble sulfonated lignin or one which tends to dissolve in water andwhich on forming the metallic salt and being oxidized is soluble. Forexample and not by way of limitation, sulfonated kraft lignin has beenfound to perform well in making the oxidized metallic salts ofsulfonated lignin according to our disclosure. This is also true ofsulfo nated soda lignin.

In deriving sulfonated lignin containing material from wood pulpingliquors varying degrees of sulfonated lignincontaining material result,depending on the well known range of conditions involved in thedifferent methods of sulfonation. For practicing our invention theresulting sulfonated raw material should be soluble in water or inhighly alkaline aqueous media and should have dispersing properties.These characteristics are in part associated with the degree ofsulfonation, or the proportion of sulfonic acid groups which haveentered the lignin molecule during the sulfonation process. The chemicalformula for sulfonic acid groups is --SO H, in which the sulfur atom iscombined directly with a carbon atom in the lignin or other organicmaterial in the lignin-containing material sulfonated.

This type of sulfur is to be distinguished from inorganic sulfates orsulfites, sulfur dioxide free or loosely combined with the lignin andsulfur which might be bound with the lignin as a sulfate. The sulfonatesulfur or sulfur combined directly with carbon is a stably bound sulfurwhich is not removed from the lignin Without drastic treatment such aswith sodium hydroxide at high temperature and pressure. In speaking ofthe sulfur content of the sulfonated lignin-containing material, Werefer to the total sulfur as the sulfur of all types which aredetermined by standard analytical procedures and to the sulfonate sulfurwhich is the sulfur stably bound with the lignin. The degree ofsulfonation required to promote solubility and dispersive propertieswill vary somewhat with the source of the lignin being sulfonated, i.e.,the conditions of pulping. However, sulfonated lignin, having sulfonatesulfur contents as low as those in the range 0.9-3.8% have been usedsuccessfully in making the dispersive additives of our invention.Products containing sulfonate sulfur in excess of these amounts do, ofcourse, have the requisite solubility for use in accordance with thepresent invention.

By way of summary, the raw material for our process is a sulfonatedlignin-containing material as it may be received from the blow pit ofthe bisulfite process or modification of said bisullite processemploying somewhat less acidity, for example and not limitation, aboutpH 4.5 instead of 1.5 or less, or other sulfonated lignin-containingmaterials such as those derived from neutral or alkaline pulp-ingprocesses. Any of these may be in any one of a number of states ordegrees of refinment, purification (3 and concentration. We prefer,however, to use concentrated and fermented spent sulfite liquor from thepulping of wood with calcium bisulfite cooking acid because suchmaterial is already sulfonated, and is easily converted to other metalsalts as disclosed hereinafter and is available in large quantities. Byfermented is meant spent liquor from which carbohydrates have beenremoved by fermentation. In any event our starting material comprises asulfonated lignin-containing material.

Our starting material may be refined and fractionated, but whether it isfractionated before or after treatment according to our inventiondepends on economical considerations and the special product desired.

Briefly stated, our novel compositions include additives produced by aprocess which in part involves converting sulfonated lignin-containingmaterial to a salt of iron, chromium, copper, and aluminum, orcombinations of said salts; or converting the refined sulfonatedlignincontaining material to said salts; or converting the fractionatedsulfonated lignin-containing material to said salts; or converting tosaid metal salts sulfonated lignin material subjected to otherpretreatments, effecting improvement in properties for use in drillingmud, for example but not by limitation, by alkaline heat pretreatment asset forth in our copending application Ser. No. 694,737, filed November6, I957, acid heat pretreatment, and pretreatment by steam stripping,gas or air blowing during heating of solutions of said sulfonatedlignin-containing materials derived from spent Wood pulping liquors.Said acid treatment may be carried out at less than about pH 4 attemperatures from 50 C. to 180 C. for times causing polymerization orthickening of the solution short of gelation, as set forth in U.S.patent application 723,036, filed December 18, 1957, as acontinuation-in-part of our US. patent application Serial No. 433,794,filed June 1, 1954, and Serial No. 539,542, filed October 10, 1955. Athigher pH, heating may be conducted at temperatures of C. to 210 C. tobring about similar polymerization or thickening of the solution shortof gelation.

Another feature of the invention comprises the use of drilling fluidadditives prepared by a process which involves subjecting the sulfonatedlignin-containing material containing said metallic salts to oxidationwhich brings about changes in the constitution of the solids of thesulfonated lignin-containing material resulting in additives of greatlyenhanced properties comparable and superior to those of naturalquebraeho in the making of drilling muds.

Also, liquor containing the said metallic salts of dissolvedfractionated components may be subjected to oxidation which brings aboutchanges in the constitution of the fractionated solids of the sulfonatedlignin-containing materials resulting also in additives of greatlyenhanced properties comparable and superior to those of naturalquebracho in making drilling muds. Our products are also superior indispersing the ingredients of clay slips, cement, plaster, etc.

The fact that the original spent sulfite liquor may be oxidized directlyand converted to the said metallic salts, forming an additive which iseffective in both fresh water and lime base muds, manifests how veryeconomical may be the products of our invention for such special uses.

Another feature of the present invention comprises the use of drillingfluid additives prepared by a process which involves the oxidation ofsulfonated lignin-containing material, regardless of whether the salt ofiron, chromium, copper and/or aluminum is formed. We have found thatsuch oxidized materials make substantial improvements in theeffectiveness of thinning of lime base drilling muds. However, saidproducts also provide substantial improvement, although to a lesserdegree than is provided by combining oxidation with salt formation, inthe case of fresh water drilling muds.

In making the salts of iron, aluminum, copper, or chromium of sulfiteliquor which, for the production of an oxidized salt, can be done eitherbefore or after oxidation, We prefer to use the sulfates of theseelements for this purpose because with calcium base sullite liquor,calcium sulfate precipitates so that it may be removed and thereby bringabout purification of the product. Higher temperature promotes thegrowth of larger crystals of calcium sulfate which are easier toseparate from the liquor, hence it is desirable to hold the liquor afteraddition of the sulfate at 9095 C. for a period of time. The formationof large crystals is also fostered by bringing about the interaction ofthe salt with the spent sulfite liquor solids in such a manner that theprecipitation of the calcium sulfate occurs more slowly. This objectivecan be accomplished by using more dilute solutions and/or using lowertemperatures during the base exchange reaction. Hence, a preferredmethod of forming the iron, chromium, copper, and aluminum salts is tocarry the reaction at 30-50 C. and then to heat the solution withagitation to 9095 and hold this temperature for one hour or longer. Thereaction mixture is usually acidic during this stage so that this lattertreatment is also an acid treatment and has beneficial action on theproperties of the spent sulfite liquor product.

Aluminum sulfate may be added preferably in proportion equivalent to thebase (i.e., calcium, sodium, magnesium and ammonium) already present inthe spent sulfite liquor or it can be used in smaller or greaterproportions. Furthermore, aluminum sulfate may be added in anhydrousform or as any of the hydrates of commerce, such as paper makers alum(17% A1 or as In making the lignosulfonate salts, we have used aluminumsulfate salts in the proportion of 1% to 50% by weight of the spentsulfite liquor solids. With the other salts, i.e., iron, chromium andcopper, the range of permissible addition is about the same, i.e., 1% to50%. For example, copper requires the addition of about 30% of CuSO.SI-I O for complete base exchange as compared with about 26% of Al(SO.,) .l8H 0 which takes into consideration the usual chemicalequivalence. However, good results have been obtained in using from toof aluminum sulfate (Al (SO .l8H O). The same observation applies to theuse of iron, chromium, and copper salts.

In addition to adding sufiicient of the cations to be equivalent toapproximately the base present in the sulfonated lignin-contalningmaterial, it is our unusual (and unexpected) discovery that an excess ofthe cation over the chemical equivalent for base exchange improves theeffectiveness of the product of our invention and discovery,particularly in respect to the conditioning of fresh Water mud inconnection with obtaining the lowest possible values for yield value and10 min. gel and water loss. Thus in the preparation of fresh water muds,we prefer to add an excess of a sulfate salt having a cation selectedfrom the group: iron, aluminum, copper and chromium, or mixturesthereof. Since these salts occur as hydrates with varying amounts ofwater, the permissible addition of these salts to the mud is moredefinitely expressed as an amount of the sulfate salt equivalent to theanhydrous form of that salt. Thus in terms of the anhydrous forms, thepermissible addition is about 1% to 80% by weight of the sulfonatedlignin, in excess of the amount of sulfate salt necessary for the baseexchange. Thus, for example, with the ferric sulfate the optimum resultsare obtained with a total addition of the sulfate salt of about 40% to50% by weight of the sulfonated lignin, which, on the anhydrous basis,would be about to 42% by weight. Accordingly, the excess over the amountfor chemical equivalence on the anhydrous basis is about 20% to 27%.Ferrous sulfate and the sulfates of aluminum, chromium and copperperform in the same manner and the excess 10 addition over the chemicalequivalent on an anhydrous basis is also about 1% to Mixtures of thesesulfate salts can be used for this purpose. Copper has the advantage ofimparting antiseptic properties to the additive, to preserve the mudwhich may be subject to micro-biological attack, particularly so whenstarch is present.

In regard to the permissible addition of excess sulfate salt thedisclosure above of l to 80% by weight of the anhydrous sulfate saltpertains to the salt and not to the oxidized salt. For the latter thepermissible addition is somewhat less than 70%. Accordingly, from thestandpoint of commercial practicability, as applied to both the salt andthe oxidized salt, an excess of l to 50% of the anhydrous sulfate salton the basis of the sulfonated lignin is preferred.

In forming the said salts of the sulfonated lignin-containing material,it is preferable to have the latter in the calcium condition, that is,as a calcium salt so that when the sulfate salts of iron, aluminum,copper and chromium are added, the base exchange reaction occurs andcalcium sulfate forms which can be removed, thus yielding an essentiallypure form of the desired salt.

The disclosure above relating to the permissible addition of l to 80%pertains particularly to sulfate salts, or any salt of said metals theanions of which form insoluble salts with calcium, for example,oxalates. However, any soluble salt of these metals could be added to asolution of the sulfonated lignin-containing material without theformation and/or removal of a precipitate. The anion in said solublesalt may be any of the common anions such as, chloride, nitrate,formate, etc., although higher concentrations of chloride ions and to alesser extent nitrate ions become deleterious above the concentrationequivalent to the base exchange capacity of the sulfonated lignin.Continuing then, when such a solution is brought to dryness, because ofthe ionic equilibrium in the solution, a mixture of salts is obtained.Thus, an amount of the desired lignosulfonate salt, for example, iron,would be present in the product, together with the base (sodium,magnesium ammonium, etc.) which was originally in the sulfonatedlignincontaining material. This product would not be as efiicient as theproduct in which the original base in the sulfonated lignin-containingmaterial was removed prior or on addition of the iron salts. However, incases where the sulfonated lignin-containing material has the basesodium, magnesium or ammonium present instead of calcium, it may besatisfactory to make the partial salt in the aforesaid manner. Thiscould be the case, for example, with sulfonated lignin from the kraftand soda processes which usually contains sodium as the base by reasonof the steps of its manufacture.

When an excess of a soluble inorganic salt (including salts such asformates and oxalates under the designation inorganic) of iron,chromium, aluminum, or copper over and above the stoichiometricequivalent of the sulfonated lignin is added in preparing the product ofour invention, and the added anions are not subsequently removed, aproduct is obtained which is less efficient as a thinner butnevertheless is effective. The lower efficiency results from (1)dilution of the thinner by the soluble inorganic salts, and (2) athickening of the mud resulting from the small amount of solubleinorganic salt added to the mud as a component of the thinner product.Thus, the thinner product with the excess appears to be inetlicient whenused in small amounts but when large amounts of said thinner product isadded to the mud, the surprising resistance of the sulfonated ligninmetal complex to the salt contamination overcomes the effect of thesmall amount of inorganic salt.

The salt contamination effect may be illustrated by considering thecombination of one part of ferric chloride with 2 parts by weight ofthinner additive of our invention. This combination would amount to 59%of excess of ferric chloride. Adding 9 pounds per barrel of thiscombination to the drilling mud gives a chloride concentration in themud approximately equivalent to 3 pounds per barrel of sodium chlorideor about 1% of said chloride and a thinner additive concentration ofabout 6 pounds per barrel. A mud contaminated with 1% salt (sodiumchloride) is readily thinned by 6 pounds per barrel of the thinneradditive.

The amount of metal for complete base exchange will depend on theconcentration of acidic components in the sulfonated lignin-containingmaterial and in particular the concentration of the sulfonated lignin.By way of example and not limitation fermented spent sulfite liquorsolids having a sulfone sulfur content of about 6% will require about ofiron for base exchange. The addition of 50% excess anhydrous ferricsulfate over that required for base exchange is equivalent to about 14%of iron.

When magnesium, ammonium, or sodium bisulfite cooking liquor instead ofcalcium has been used in manufacturing the pulp, it is then desirable,but not absolutely necessary, to eliminate or partially eliminate themagnesium, ammonium, or sodium ions prior to making the iron, chromium,copper, or aluminum salt. This situation can be brought about byconverting to the calcium salt before proceeding with the process of ourinvention, or it can be accomplished by any number of procedures wellknown to those skilled in the art-for example, by ion exchange, dialysiswith addition of acids, and base exchange procedures in general. Forexample, cations (i,e., magnesium, ammonium, or sodium) may be removedby passing the liquor through a cation exchange column in the hydrogenstate, and then treated with an oxide or hydroxide of iron, chromium,copper or aluminum. We prefer to have the lignosulfonate in the form ofthe calcium salts before making the iron, chromium, copper, and aluminumsalts because the salts are obtained with less contamination in thismanner by reason of the calcium sulfate being precipitated so it can beremovedbut note well, such purified products can be obtained by anyprocedure known to the art for making the conversion to the desired saltas well as those named immediately above.

An example of partial salt formation comes as a result of the oxidationtreatment with sodium or potassium dichromate as a result of the factthat chromium salts are a product of the reactions involved. Any solublechromium salts thus formed will provide chromium ions which will be inequilibrium with the calcium ions a sociated with the sulfonate group ofthe lignosulfonate. Thus, a partial chromium salt of the lignosulfonatein essence will be formed which would tend to impart the propertiesattained if the calcium were removed and the lignosulfonate salt werewholly chromium salts. If, furthermore, an excess over the amount ofsodium dichromate necessary for the base exchange, i.e., about 12% ofsodium dichromate, is added, additional chromium ions resulting from thereduction of the dichromate are present which tend to drive the reactionin the direction of the formation of the chromium salt of thelignosulfonate so that this excess would have somewhat the effect ofremoving the calcium or in other words, form ing a chromium salt insteadof the calcium salt of the lignosulfonate. The addition of excess sodiumdichromate, would also result in an excess of chromium salts formed bythe reduction of the dichromate and would have somewhat the effect ofthe addition of an excess of chromium sulfate over that necessary tomake the base exchange. This method of forming the salts, however, doesnot yield a product which is as effective for mud formulation as themethods previously described where calcium is removed, for example asthe sulfate or otherwise, because calcium ions cause thickening ofdrilling mud and because of the miscellaneous reaction products.However, the efiectivencss of agents made in this manner can be improvedby removing the calcium during the treatment, for example, by addingsulfuric acid or any other acid Whose anion forms insoluble salts withcalcium or by addition of suitable salts which form insoluble compoundswith calcium such as sodium sulfate. This illustration is mentioned byway of example that an improvement can be obtained by the presence of anexcess of chromium, aluminum, copper, iron salts or combinationsthereof, even though there is an equilibrium mixture present with otherions, such as potassium and sodium, but is not given to indicate apreferred method of operation.

It should be noted that an excess of sodium ions resulting from excesssodium dichromate addition is not seriously harmful since the drillingmud clays are also sodium salts and the additional sodium ionsintroduced into the mud by the additive are relatively few.

The iron, chromium, copper, and aluminum salts of the iignosulfonatesthus formed are useful as drilling mud thinners in muds which do notcontain an excess of lime, i.e., fresh water muds, and these productsare thereby distinguished from the spent sulfite liquor productspreviously used as thinners in the so-called lime base muds. Theseprevious lignosulfonatc thinners which may be ammonium, sodium,magnesium, or calcium salts of lignosulfonates are operable only in thelime base muds and are not effective in muds which are sometimes termedfresh water muds, i.e., muds of low pH and which do not contain salts ofaluminum, iron, cooper and chromium--the inclusion of said salts being apart of our invention and discovery. The aluminum, iron, copper, andchromium salts of the spent sulfite liquor on the other hand areeffective in varying degrees over the whole pH range of the fresh Watermuds and are also operable as thinners in lime base muds.

Furthermore, let it be noted that another alternate pretreatment may beused whereby the hot spent sulfite liquor is acidified and air blown ortreated to remove the sulfur dioxide and then oxidized with the agentsdescribed below. By this course the spent sulfite liquor is purified ofsulfur dioxide, and apparently the structure of the components of thespent sulfite liquor is modified and the oxidizing agents if later usedare conserved for performing their special functions.

As heretofore indicated an important feature of our invention anddiscovery is that the oxidation of spent sulfite liquor components leadsto increased activity or enhanced properties of said componentsrespecting dispersing properties, and that these changed properties aremanifested in the thinning of the viscosity of clay suspensions and alsoin the reduction of the gel-like properties of such suspensions. We havefound that most oxidizing agents are operable in varying degrees as tothe improvement produced. Particularly effective for this purpose arethe following: hydrogen peroxide, ozone, lead dioxide, chromic acid,chlorine, alkali and alkaline earth hypochlorites, alkali metalchromate, alkali metal permanganate, alkali metal persulfate, alkalimetal perborate, and electrolytic oxidation. These several agents arethe preferred oxidizing agents.

The preferred forms of the oxidizing salts such as chromates,permanganates and persulfates are the sodium and potassium salts, butthe ammonium salts may also be used and where available are included inthe descriptive term alkali metal salts.

When chromate is used for oxidation of spent sulfite liquor, thechromate is added preferably as sodium dichromate, since this form isthe most readily available in commerce, and in subsequent discussionsthe chromate addition is referred to as dichromate. However, it is wellknown that in aqueous solution chromate ions (CrO and dichromate ions cro, are readily interconvertible, depending on the pH of the solution. Instrongly acid solution, the dichromate ion predominates, but onneutralization with alkali the dichromate shifts to the chromate.Equilibrium is readily reached between the two forms, depending on thepH of the solution. Therefore the chromate may be added as eitherchromate or dichromate.

Further in regard to oxidation with chromium compounds: By experiment,we have discovered that oxidation of fermented spent sulfite liquorsolids with sodium chromate at pH 8 provides a product which hassubstantially the same thinning effect on the drilling mud as a productobtained by oxidation with sodium dichromate at pH 4. In making thisexperiment both products were converted to the iron salt to make the mudtest. Furthermore chromic acid may be used instead of the chromates inwhich case it is usually necessary to add sodium hydroxide to neutralizethe product to about pH 4 to 5 prior to drying. All of these chemicals,i.e., sodium chromate, sodium dichromate and chromic acid give oxidizedproducts, the iron, aluminum, copper and chromium salts of which areeffective thinners for both lime and fresh water muds and givesubstantially similar results.

One method of obtaining oxidation is by electrolysis whereby oxidationtakes place at the anode of an electrolytic cell. can be obtained in asimple cell with or without a membrane to separate the anode andcathode, and improved products have been obtained with current usagesfrom a desired effective amount up to about 5 ampere hours or more pergram of sulfonated lignin-containing material. It will be understoodthat the amount of impurities or contaminants, including carbohydratesand sulfur dioxide, in the sulfonated lignin-containing materialelectrolyzed, will change the electrical current consumption (i.e.,ampere hours per gram of said :sulfonated material) to obtain a givendesired result. Thus we have found that from about 0.2 to 5.0 amperehours per gram is suitable for fermented spent sulfite liquor but lesscurrent consumption will be necessary for more purified sulfonatedmaterial while greater current consumption may be necessary for lesspurified sulfonated lignin-containing material.

The electrolysis should be conducted under conditions which will bringabout oxidation and not reduction. For this purpose a non-reactiveanode, that is, an anode which does not dissolve substantially duringthe electrolysis, should be used. Thus platinum is suitable. Also, it ispreferable to carry on the electrolytic oxidation prior to forming alignosulfonate salt of the metal iron, aluminum, copper and chromium.However, if the salt is formed before electrolysis, any metal lost forexample by plating on the cathode should be replaced, that is theequivalent of such lost metal should be readded to the electrolyzedsolution. This loss of metal ions may be substantially eliminated byelectrolyzing under acid conditions of below about pH 3, or as statedabove, by electrolyzing before forming the said salt.

Oxidation by addition of sodium perborate results in contamination ofthe product with sodium borate which must be removed to obtain thegreatest efficiency of the product. One method of purifying the productis to remove the resulting borate ions as calcium borate which readilyoccurs if the starting material is a calcium salt of sulfonatedlignin-containing material. The sodium perborate has an alkalinereaction and raises the alkalinity of the solution sufiiciently to makecalcium borate insoluble. The calcium borate may be removed by filteringor settling. Other methods known to those skilled in the art can be usedfor such purification. As set forth herein, chlorination also results inby-products of the reaction which should be removed by purification toobtain more effective products for drilling mud thinning.

In regard to the choice and use of oxidizing agents for practicing ourinvention, two factors are of prime importance: The strength or power ofthe oxidizing agent and the quantity of oxidant being used in proportionto the organic solids being oxidized. The strength or intensity of theoxidizing agent is expressed as an oxidationreduction potential, andtables of these potentials are We have found that effective electrolysisavailable in the chemical literature. We have found that the oxidizingagents which are suitable for carrying out our invention have a range ofoxidation potentials greater than -l.3. The quantity of oxidant which isused to bring about the desired result may be expressed as the weight ingrams of each oxidant which can be used per grams of sulfonatedlignin-containing material.

The amount of oxidant required depends on the specific oxidant beingused, the nature and purity of the sulfonated lignin-containing materialbeing treated and the conditions under which the treatments areconducted. In general and for practical operation, particularlyrespecting cost, 1% to 50% by weight of the several oxidunts on thebasis of the dry sulfonated lignin-containing material is all that isrequired to produce the desired result. However, when the oxidant is ofa less concentrated character, as in the cases of alkali persulfate andperborates, both being costly, a large percentage of such oxidant isrequired to obtain the desired result. in any case, the reaction shouldbe conducted in such a manner and with concentrations and proportions ofthe reactants so that gelation of the solution does not occur and apermanently soluble product is obtained. Solubility of our additiveproduct is a fundamental requirement because Lhe product is to be addedto a drilling mud system, one component of which is water in which theadditive product must dissolve to function as a thinner. Also, thedissolving brings about the distribution of the agent uniformlythroughout the medium which increases the effectiveness of the product.

By way of explanation gels contain some occluded water soluble productand to the extent that the water soluble component is available or thegel dissolved in the medium said gels function somewhat as thinners. Ifany thinning action occurs with gelled (ie. insoluble) products, suchthinning is deemed not to be due to the gel functioning as a surfaceactive agent but is due to the soluble component accompanying the gel.At higher pH, i.e,, above about, the unwashed gelled products dissolveto some degree and show some tendency to thin the mud. Particularly isthis true if the dissolved componcnt is not washed out. In any case gelsare not desirable because the material is less efficient.

Permanently stable solutions without gelation as shown in the examplesmay be obtained by conditions which slow the rate of reaction and keepthe reactants in low concentration in relation to each other.Furthermore, other conditions affecting the formation of gels in more orless degree are the degree of sulfonation, the concentration of thesulfonated lignin containing material, temperature, concentration of theoxidant, pH and effectiveness of mixing. In addition, the character ofthe sulfonated lignin containing material being treated affects theamount of oxidant being used, in particular, the degree to which thematerials have been previously purified, especially of reducingsubstance such as sulfur dioxide and carbohydrates, and/or fractionated.The degree of sulfonation is important in regard to water solubility.Also, we have discovered that the molecular weight, and apparently themolecular weight distribution within the fraction will affect thequantity of oxidant required to bring about the desired result. By wayof example and not limitation. when a 5% to 50% solution concentrationof fermented spent sulfite liquor solids is being used as much as 15% ormore of hydrogen peroxide may be added, whereas, with potassiumpermanganate or potassium dichromate, such concentration of spentsulfite liquor thickens rapidly to a gel when about 10% of these agentsis added. Furthermore, by Way of example to show the effect that theprior history or character of the spent sulfite liquor has on thequantity of oxidant which may be used without causing gelation, when acaustic treated fermented spent sulfite liquor as described in ExampleXIV is used at pH 4, about 8% of sodium dichromate will cause gelationat 42% total fermented spent sulfite liquor solids,

15% of sodium dichromate will cause gelling at solids and 21% of sodiumdichromate at 12% total solids, the dichromate in each case being addedas a 25% solution in water at 60 C. Let it be noted that the abovepercentages are based on the weight of the dried fermented spent sulfiteliquor solids being treated. Moreover under other conditions, even moreof this oxidant can be added without causing permanent gelation or lossof water solubility. Purification and molecular weight are other factorswhich bring about gelation with diiferent proportions of the oxidant.For example, using a solution of 45% to 50% total solids, about 4% byweight of the solids of the oxidant will gel the purified high molecularweight lignosulfonates at a pH of less than 4.5, whereas, as much as 8%or more of potassium permanganate or sodium dichromate may be added tothe low molecular weight lignosulfonate fractions of the sameconcentration without gelation. But substantially larger concentrationsof sodium or potassium dichromate may be added if the reactants aredilute. For example, a low molecular weight lignosulfonate fraction (40%of the total original fermented spent sulfite liquor solids) containing17% of reducing substances expressed as glucose as a 2.5% solution inwater treated at room temperature with 5 by weight of sodium dichromateas a 2.5% solution at a pH of 3 yielded after drying at room temperaturea product which was slowly soluble in water. With 40% by weight ofsodium dichrornate the product was rapidly soluble in water. During suchreactions the pH rises and acid such as sulfuric may be added tomaintain the desired pH. The reaction under the above conditions wassubstantially complete in one hour. Thus the objective, namely a Watersoluble oxidized product, can be obtained with up to 50% by weight ofthe dichromate oxidant depending on the conditions used in the reaction.Similar results are obtained with potassium and sodium permanganate. Theother oxidants Which are less subject to providing insoluble productsmay also be used up to 50% and more by weight of the sulfonatedlignin-containing material depending upon said conditions.

PILOT TEST We have discovered that the oxidants which are suitable foroxidizing the sulfonated 1ignincontaining material may be roughlydivided into two groups: Those containing the metal ions chromium andmanganese, i.e., the alkali metal chromates and the alkali metalpermanganates and those involving gaseous oxidation components, such ashydrogen peroxide, sodium persulfate, sodium perborate and chlorine and,accordingly, different tests were originally necessary in establishingthe maximum amount of the oxidant which could be used for any particularsulfonated lignin containing material.

The maximum amount of oxidant particularly the chromates andpermanganates which can be used with any one sulfonated lignincontaining material can be determined by the following pilot test. Adissolved sample of the sulfonated lignin containing material is dilutedto 2.5% solids, acidified to pH 3.0 with sulfuric acid for thisparticular test and various amounts of sodium dichromate added, togetherwith sulfuric acid to maintain pH 3.0. The solutions are then allowed tostand about 1 hour at room temperature, adding sulfuric acid atintervals to maintain pH 3.0. At the end of 1 hour, the sample is heatedto 80 to 90 C. and digested at this temperature for about an hour. Theproduct samples are then dried at 60 C. and tested for solubility inWater. The highest amount of dichromate giving a soluble product is themaximum limit of the amount of oxidant that can be used.

Another guiding test as to the maximum quantity of oxidant which may beused with any one sulfonated lignin containing material in forming theproducts of our inven tion and discovery is an evaluation of theperformance of the product as a thinning agent for drilling mud. Toapply this test, a solution of about 10 grams of sulfonated lignincontaining material dissolved in 10 cc. of water is treated with 2 gramsof ferric sulfate to convert the lignosulfonate to the iron salt, thesolution heated to 80 C. and centrifuged to remove caicium sulfate. Thissolution is then treated with various amounts of the oxidant beingtested at a pH of about 3 to 5 for this particular experiment and heatedat 8090 C. for about I hour and then dried at 60 C. The product istested for solubility in water, as above, and then for mud thinningproperties as described herein. If the properties of the base mud arenot improved by the addition of the product, then too high aconcentration of that particular oxidant was used in the oxidationstage.

In using the oxidizing agents which evolve a gas in the oxidationprocess, such as hydrogen peroxide, chlorine or sodium persulfate, agreater amount than that equivalent to sodium dichrom ate or sodiumpermanganate is required, since the use of such agents involves a morerapid deterioration and possible escapement of gas without completereaction. It is probable also that the polyvalent metals manganese andchromium contribute to the effectiveness of the final product and theseare not present in said other oxidants. Therefore, while the equivalentproportions are a guide to the relative amount of oxygen that can beused, they are not exactly equivalent in regard to the improvement whichequivalent amounts of each of the oxidants will produce in the product.

Optimum thinning properties appear to be attained with sodium dichromateusages which give solutions well removed from the point of gelation. Fora fermented spent sulfite liquor, of to total solids, the preferredamount of oxidant is about 7% to 9% of sodium dichromate based on thespent sulfite liquor solids for overall performance respeeting theseveral properties required in drilling mud, but especially low waterloss characteristics have been observed with about 18% of sodiumdichromate. On the other hand, with chlorine which is considered anoxidizing agent herein, substantially more than the other agents can beadded because some of the chlorine reacts by substitution with the spentsulfite liquor components, so that additional chlorine is required tobring about the desired oxidation results.

The time and temperature of the reaction is important in that thereaction should be allowed to go essentially to completion and theproduct should be substantially free of gels. It is preferable that theoxidation be controlled to yield a solution which can be dried to apowder which can be redissolved in water. If the oxidation is too severethe solution may gel or the dried solids may not be water soluble.Potassium permanganate and potassium diehromate are very rapid in theiraction and usually the oxidation is complete in 5 to 20 minutes andthereafter the solution is stable and shows no visible evidence ofchange on standing. If 10% of these agents are added as a 25% solutionto concentrated liquor or greater than 40%, the spent sulfite liquorwill gel in 15 minutes at room temperature, or if the solution is hot,the gelation will occur almost immediately. Solutions more dilute inorganic solids, permit the addition of higher percentages of theseoxidants. With milder oxidants, such as hydrogen peroxide, 15 minutes to24 hours are necessary to bring about the completion of the oxidation.The temperature is usually a matter of choice and convenience but shouldbe such that the reaction is complete in the time provided, althoughlower temperatures will give less difficulty with local formation ofgels.

The concentration of the spent sulfite liquor can be any concentrationup to by weight of solids, but it is desirable to have the concentrationof the liquor low enough to promote homogeneous reaction and preventsubsequent gelation. However, for practical reasons, it is preferred touse solutions of as high concentration as possible and, preferably, ofthe order of 40 to 50% solids concentration. For this reason, the dilutesolution of the oxidant is added to the cool spent sulfite liquorsolution of 40 to 50% solids With intensive mixing and after thereaction has been more or less completed, the solution is heated to thetemperature at which drying will be conducted.

Thus, it is clear that, because of the choice of oxidants involved inproviding required properties, the varied nature of the sulfonatedlignin containing material, and the many factors involved in thephysical conditions under which the reactions can be conducted, and alsothe many well known types of equipment used in mixing the reactants,that it is not feasible to set forth the exact operating conditions foreach product of production. Furthermore, the factor of what mud propertyis most desired must be considered since the properties do not respondin a parallel manner to all treatments. That is, sometimes all theproperties may be improved whereas in some cases only one of theproperties may be improved. Accordingly, a selection must be made toobtain the desired re- :sult. But many examples are given in the hereindisclosure which will enable persons skilled in the art to selectconditions of treatment best suited to the particular re quirement ofthe case in hand. But for most cases for use in the field the oxidantscan be used in the concentration of l to 50% by weight of the organicsolids as herein disclosed and thereby obtain a fully reacted andsoluble product without gelation. The determination of the maximumamount of any given oxidant which can be used for any particularsulionated lignin-containing material is determined by pilot tests ashereinbefore described. But the usage is one depending upon which mudproperty is most desired.

Special processing is necessary when chlorine is used as the oxidizingagent since in addition to oxidation and any other reactions whichoccur, there is a reaction of chlorine with the sulfite liquorcomponents, and there are byproducts from the reaction such ashydrochloric acid, which if left in the product may have a deleteriouseffect. For example, it has been found that on the addition of 1% to 4%of chlorine on the basis of the dry weight of the spent sulfite liquorsolids, the properties of the sulfite liquor residue improve evenwithout further purification to remove the end products formed, such ascalcium chloride. The chlorination can be increased up to the additionof 45% of chlorine above which the chlorinated lignin tends to becomeinsoluble in the strong hydrochloric acid and calcium chloride solutionformed in which case it is necessary to further refine the products byremoving the hydrochloric acid and reaction products. One of the bestmethods of accomplishing this purpose is to precipitate the chlorinatedlignin with lime. This treatment has additional benefit of purifying thelight)- sulfonates not only of the hydrochloric acid and its endproducts, but also of the carbohydrates themselves. In this connectionwe have discovered that, whereas with regular spent sulfite liquor it isdiflicult to divide the lignosulfonates into several fractions bytreatment with lime, surprisingly with the chlorinated lignins of ourinvention and discovery, the products can be divided very readily intofractions of different average molecular weight. This finding has beenof extreme usefulness in the preparation of specific fractions of thechlorinated lignin as to molecular weight.

It has been known that lignosulfonates may be precipitated in mass fromspent sulfite liquor by adding at one time relatively large quantitiesof lime slurry until a pH of 11-12 is reached. It is our discovery thatthe lignosulfonate can be precipitated and recovered as fractions ofdifferent molecular weights by adding the lime in small increments.Especially surprising and useful is our discovery that if thelignosulfonates are treated with chlorine then they may be more readilydivided by lime precipitation into many small fractions, while at thesame time purifying the lignosulfonates from the carbohydrates,chlorides, and other miscellaneous components of the sulfite liquor. Theoxidized and chlorinated lignosulfonates, fractionated as to molecularweight by lime, may then be used as such as lime base mud thinners, orthey may be converted to aluminum, iron, copper, and chromium salts andas such they also make highly effective fresh water drilling mudthinners. Such oxidized and chlorinated lignosulfonates may be convertedto other salts such as sodium, magnesium, ammonium, etc. if calcium isobjectionable in the product. Fractionation of the chlorinated spentsulfitc liquor can also be accomplished by the alcohol fractionationprocess according to the disclosures of our application Serial No.437,833.

In summary, our invention comprehends the discovery that oxidation withor without forming a salt of a metal selected from the group of iron,aluminum, copper, and chromium of the lignin sulfonatecontainingmaterial provides an improved drilling fluid and that the amount ofoxidation can be greatly varied.

The oxidized products are useful as thinners, and this is particularlyimportant because products can be prepared from the original spentsuliite liquor merely by a simple oxidation process to give productsequivalent as thinners to those prepared by more complex and expensiveprocedures. Furthermore, let it be particularly noted, essentially inprecipitation and fractionation procedures only a part of the spentsulfite liquor solids are available for use as mud thinners while, incontrast, our invention and discovery makes use of substantially all ofsuch solids. This point is important where yield and costs are of primeconsideration.

In general, the products of our invention and discovery may be preparedfrom spent pulping liquor and the solids therein in the condition asreceived directly from the di gester, or said products may be preparedfrom modifications of the said solid components of the spent pulpingliquor. Such modifications may be provided by various treatments but,nevertheless, the resulting solids still do constitute solublesulfonated lignin-containing materials. By way of example and notlimitation the treated solids may be as follows: They may be as theyexist after fermentation of spent sullite liquor whereby thecarbohydrate content is reduced or they may be as solids after hot spentsulfite liquor is acidified and air blown; or they may be obtained asset forth in U.S. application Ser. No. 391,116, which briefly states thespent sulfite liquor treated with an inorganic base, for example sodiumhydroxide, in developing a final pH of 7-10, the same may be heated at49 to C. for a period of 30 minutes to 2 weeks, the solid organiccomponents being maintained in solution throughout the said reactionperiod; or the spent sulfite liquor may be essentially freed ofcarbohydrates and extraneous material by any one of a number ofprocedures, preferably by fermentation or by adding increments of lime,or by precipitation, dialysis, separation by organic solvents, and/ ororganic buses, or precipitated as basic lignosulfonate for example withlime, or by salting out with salts such as calcium or sodium chloride.

Furthermore, the spent sulfite liquor components may have been derivedby the pulping with agents other than the usual magnesium, sodium,ammonium, and calcium bisuliites. These other agents disclosed hereinare iron and aluminum bisulfites.

Oxidation treatment improves the spent sulfite liquor components inproviding a more effective lime mud thinner or more effective thinningand dispersing action in general, i.e., in both lime base and freshwater muds.

Base exchange to form iron, aluminum, chromium, or copper salts enhancesfresh water mud thinning properties, and improves some of the lime mudproperties, as for example a. base exchange with aluminum sulfate willyield a product with lower viscosity and gel characteristics in limemud.

Preferably Concentrated to 30%-50% Solids) l Acid Salt 4) Oxidized lAlkaline (7) Acid 1) (see Appl.S.N.694,73T) New Oxidlze (3) Oxidizc(441) Salt (6) tralizc Al,Cr,l. e,Cu Acidity 3) Alum or (11) with Salt.(3a) lurrlc base (2) Al,Gr,Fe,Cu OXKilZO (El) buliate limo mud thinnerOxidlzc (l2) Al salt i or go in l Fraetionato Manifestly, if thestarting material was either raw in the case of acid treatment. Thisoxidized product may spent sulfite liquor as it comes from the blow pitor if it was fermented spent sulfite liquor without further purificationor fractionation, then any of the products of our invention as set forthin the above outline of the possible manifold treatments Within ourinvention, may be further purified or fractionated by adding smallincrements of lime as herein disclosed or by solvent fractionation,application Ser. No. 437,833, filed June 18, 1954, and now abandoned infavor of US. Serial No. 703,664. Let it be noted that fractionation ofthe spent sulfite liquor provides for selection of fractions to yielddesired properties in the additive formulated as disclosed herein.

Thus, to follow through in detail, the starting material may be, aspreviously discussed, either the spent sulfite liquor solids ascontained in the spent liquor as received from the blow pit, or thesesolids refined in various manners, such as by fermentation, limeprecipitation, fractionation, etc. In any case, the solids to be treatedare preferably concentrated to to 50% solution. One method of operation,following from point (1.) on the chart, is to treat the concentratedliquor with an acid and heat for example for l to 2 hours at 95 to Iii-0C. At this point if calcium sulfate is precipitated, it may beseparated, depending on the purity desired in the final product. Saidacid treatment may be carried out at less than about pH 4 attemperatures from 50 C. to 180 C. as more fully set forth in ourco-pending application Ser. No. 723,036 (U.S.).

This product can be neutralized with a base such as sodium hydroxide (wemean a compound which yields hydroxyl ions in solution) to a pH above3.5 so that it can be dried without degradation and then used as such asa limed mud thinner (2) without further treatment; or it can be furtherimproved by oxidation, preferably with an alkaline reagent such aspotassium permanganate or sodium dichromate as indicated at point (3) inthe outline. Either product may be used as a liquid, or it can bereduced to solids by evaporation and drying. In either case, theseproducts may be used as thinners for drilling muds. Alternatively, theproduct can be converted to the salt (3a) of iron, chromium, copper, andaluminum, and this is outstanding in the fact that the thinning actionis improved for both fresh water and lime base muds.

Again, the acid treatment may be carried out with an acid salt such asferric sulfate, aluminum sulfate, chromium sulfate, or copper sulfate insuch proportions as to also effect a base exchange (4) and yield aproduct which is effective for thinning all types of water base drillingmud. This product may also be oxidized (4a) to obtain furtherimprovement in mud thinning properties.

Rather than treating with an acid as in (l), the concentrated liquor maybe treated directly with an oxidizing agent as in (5). In this case someof the oxidizing agent is required to oxidize the sulfur dioxide whichescapes be used as a mud thinner, particularly as a lime base mudthinner, or it may be converted to the iron, aluminum, copper, orchromium salt as in (6) whereby the properties are unexpectedly enhancedfor thinning both lime base and fresh water muds.

Another pretreatment, which gives improvements in the sulfonatedlignin-containing material preparatory to following the procedures ofour invention, is the heating of the solution of the sulfonatcdlignin-containing material in water solution at highly elevatedtemperature and at a pH greater than 4 and preferably about 7 to 10. Theheating is carried out for a short period of time above a temperature ofC. and of the order of 30 minutes at a temperature of about 200 C. At220 C. the lignosulfonate becomes partially insoluble in water andgel-like and is not suitable for further use for the purpose of makingdrilling mud thinners. This heating is conducted while blowing thesolution with a gaseous medium such as air or nitrogen. Productsprepared in this manner have improved properties, said improvement inproperties being somewhat equivalent to those attained by our process ofacid treatment as described in our U.S. Ser. No. 723,036.

Another and highly effective procedure is to follow the process outlinedin our application Ser. No. 694,737 in volving treatment with alkali.This product (7) may then be acidified either with an acid (8) andoxidized (9), whereby a drilling mud thinner particularly effective forlime base muds is obtained, or further processed to form the aluminum,iron, copper and chromium salt (10). Instead of acid, aluminum, iron,copper, and chromium sulfate may be used through which an economical andeffective spent sulfite liquor additive (11) is produced, the propertiesof which may be greatly enhanced by oxidation with any of the oxidizingagents previously mentioned, to yield (12) an extremely effective agentfor conditioning all types of water base drilling fluids, such as, freshwater, lime base, gypsum and oil emulsion types.

NB. We have discovered that spent sulfite liquor components, or suchcomponents chemically modified in their separation from spent sulfitcliquor, or in their preparation (i.e., we find that materials identifiedin general as lignosulfonates respond favorably to our treatment) aregreatly improved in their effectiveness as dispersing agents and for usein drilling muds by treating them with one or both of the followingsteps:

(1) Oxidizing said spent sulfite liquor components.

(2) Treating to form a salt having an element selected from the groupconsisting of iron, aluminum, chromium, and copper.

The order of the above steps or treatment (oxidizing or forming a salt)is immaterial.

Continuing our treatment against contamination by calcium sulfates, theproduct resulting from both steps 1 and 2, or the product of step 2, istreated with a salt in the proportion of 1% to 100% of thelignosulfonate solids of said spent sulfite liquor solids, selected fromthe group consisting of sodium sulfate, sodium sulfite, potassium sodiumtartrate, sodium oxalate, sodium phosphate, sodium carbonate, sodiumbicarbonate, aluminum sulfate, iron sulfate, and their correspondingpotassium compounds and mixtures thereof.

Method of testin -Specific examples of treatment, together with tablesshowing results of tests of the materails, will now be set forth. Themethod of making the tests is that commonly followed in the drillingindustry.

The sulfonated lignin additives of our invention may be used in manyways, but chief among these is that revealed in drilling muds. For thispurpose a material is required which will bring about a lowering inviscosity of the complex clay suspension which is termed the drillingmud, and will also serve to decrease its gel strength and water losscharacteristics. The accepted methods for evaluating materials toascertain their utility for drilling muds are described in thepublication entitled American Petroleum Institute Code 29, ThirdEdition, May l950 Recommended Practice on Standard Field Procedure forTesting Drilling Fluids. This manual is prepared and published by theAmerican Petroleum Institute, Division of Production, Dallas, Texas, andis used throughout the industry for testing drilling muds.

In making the laboratory tests on drilling muds according to theprocedures mentioned above, it is necessary to use a clay or combinationof clays. In general, clays are of extremely wide distribution in theearth's surface and are complex and difiicult to define chemically. Forexample, H. A. Ambrose, Ph. D. and A. G. Loomis, Ph. D., state regardingdrilling mud clays: analysis tells us little with respect to theproperties required in drilling. There has been no correlation betweenchemical analysis and clays and their suitability for drilling purposes.The Science of Petroleum, volume I, page 458, 1938, Oxford UniversityPress (London). Although clays have been divided into several classesaccording to their chemical and physical form, the materials encounteredor used in drilling muds are mixtures of said clays and so it has becomepractically accepted to define these materials in terms of What istermed yield value. According to practice then (Principles of DrillingMud Control, 8th edition, pages 2 and 3, published by the AmericanAssociation of Oil Well Drilling Contractors, Dallas, 1951) clays aredefined in terms of yield value, which is the number of barrels of 15cp. mud that can be prepared from a ton of material along with water.Thus in the examples, we refer to the use of natural clay and define theyield value to characterize the type of clay which would give similarresults.

By following the standard methods identified above and using clays ofdefined yield value, the efficacy of the sulfonated lignin additives ofour invention is measured in terms of initial gel strength, viscosity,ten-minute gel strength, and water loss.

The Stormer viscometer has been used almost universally in makingviscosity measurements according to the standard methods of the AmericanPetroleum Institute. Also let it be noted that another means ofmeasuring viscosity is a motor driven rotational viscometer known as theFann V-G meter (viscosity-gel). This instrument measures two factors ofviscosity called yield value of fluids and plastic viscosity which areso related that two times the plastic viscosity plus the yield value isproportional to the viscosity at 600 rpm. Since the plastic viscosity isessentially constant for any one mud, the variation of the yield valuesindicate directly the variation of viscosity and therefore the yieldvalue is reported in the tables where the measurements were made withthe Fann instrument.

Generally only the yield value of the drilling mud is affected by theaddition of thinners. Yield values are reduced by drilling mud thinnersbut plastic viscosity is affected very little. The plastic viscosity canonly be changed by adding to or removing water from the mud. The FaunV-G meter type of instrument is preferred for drilling muds since itindicates whether thinners are needed to lower yield or whether water isneeded to decrease plastic viscosity.

The viscosity factor yield value of fluids defined above should not beconfused with yield value of a clay which has been defined hereinaboveas the number of barrels of 15 cp. mud that can be prepared from a tonof clay along with water.

Mud rest procedures.-The following mud test procedures describe indetail the mud preparation and testing procedures used. The claysdefined in the test procedures given below were used in all of the firsttwelve examples except Examples II and III in which another but similarclay was used having a yield value of 36, that is. the clay would yield36 barrels of i5 cp. mud per ton of clay. Clays in other examples aredefined therein but have about the same yield value.

Lime mud test procedure.Sixty grams of a commercial rotary drilling claywith a yield value of 45 barrels of 15 centipoise mud per ton of claywere mixed with 325 milliliters of distilled water in a Hamilton BeachNo. 30 Drinkmaster mixer for 15 minutes at 15,000 r.p.m., and then agedby rolling, i.e., agitating in pint bottles overnight at roomtemperature. The aged mud was broken over to a limed mud by adding 6grams of calcium hydroxide, 6 milliliters of sodium hydroxide solutioncontaining 0.25 gram sodium hydroxide per milliliter, and the sulfonatedlignin containing material additive to be tested (each gram addedequivalent to 1 pound per barrel) and mixing for 5 minutes at highspeed. Broken over is a term used in the industry to denote theprocedure and the accompanying change in properties which occur when anexcess of calcium hydroxide and sodium hydroxide is added to a clay withintimate mixing as next above set forth. The mud was then re turned tothe bottle and again rolled overnight at room temperature, and finallymixed another 5 minutes immediately before determining viscosity, gelsand Water loss by the standard procedure of the American PetroleumInstitute.

Fresh water mud lest procedure-Thirty grams of a commercial sodiumbentonite rotary drilling clay with a yield value of 92 barrels of 15centipoise mud per ton of clay were mixed with 335 milliliters ofdistilled water in a Hamilton Beach No. 30 Drinkmaster" mixer at 15,000rpm. for 15 minutes and then aged by rolling overnight in pint bottlesat room temperature. The thinner additive (each gram added equivalent to1 pound per barrel) and sodium hydroxide to give the desired pH werethen added, the mud mixed 5 minutes, and again rolled overnight at roomtemperature. A final 5 minute mix was made immediately before measuringviscosity, gels, and water loss by the standard methods of the AmericanPetroleum Institute. The mud may he returned to the bottle and rolled afurther 24 hours at F. and then retested to obtain information on theeffect of temperature. Higher temperature aging is described in ExampleXVII.

Gyp mud test procedure.-The gyp (or gypsum base) mud test procedure isthe same as the fresh water mud test procedure except that 6 grams (eachgram added equivalent to 1 pound per barrel) of plaster of Paris (CaSOJ/QH O) were added together with the thinner additive, and the mud wassubsequently mixed for 20 minutes instead of 5 minutes.

Oil emulsion test procedure-The base mud is prepared as described aboveand may be any of the types 23 such as lime base, gypsum, fresh waterand salt water muds. After adding the thinner additive being tested andmaking the standard tests for gels, viscosity and water loss, to 20% byweight of diesel oil is mixed into the mud with a high speed mixer at15,000 rpm. and the resulting oil in water emulsion mud tested for gels,viscosity and Water loss by the standard API procedures. Note that theterm thinner is used in the art in reference to agents or additives forreducing the viscosity of drilling mud.

EXAMPLE I This example illustrates the improvement in mud thinningproperties resulting from heating spent sulfite liquor to a hightemperature and simultaneously blowing with air or an inert gas. By wayof example and not limitation, the lime mud thinning properties of asample of fermented spent sulfite liquor heated at 200 C. while blowingwith argon were compared with the said properties of the original spentsulfite liquor and those of said liquor heated at the same temperaturefor the same time Without blowing. In addition, the iron salt of theheated and gas blown product was compared with the iron salt of theoriginal spent sulfite liquor as a thinner for gypsum base muds to showthat the improvement in thinning properties as a result of the heattreatment is manifest in other types of muds than lime muds. Oxidationof these heat treated samples as described herein iabove brings aboutfurther improvement in the thinning propertie-s.

Concentrated fermented calcium base spent sulfite liquor (2.18 g.)having 40% by weight of non-volatile solids was neutralized to pH 6.3with sodium hydroxide and heated to 200 C. in a pressure vessel fittedto permit bubbling gas through the liquor. Sixty-five grams of argon wasbubbled through the liquor in 38 minutes, the vessel was cooled and theproduct liquor dried for testing. The product liquor had a pH of 5.3.

A second sample of the neutralized liquor was heated at 200 C. for 30minutes in a sealed bomb as a control to determine the effect of heatingalone.

Mud tests were made as herein before described using a mud having 45.5lbs. per barrel of a mixture of clays containing six parts by weight ofa commercial drilling clay having a yield value of 45 barrels of op. mudper ton and 1 part by Weight of a commercial drilling clay having ayield value of 95 barrels of 15 cp. mud per ton of clay.

With reference to Table 1 of Example I heating the liquor at 200 C. for30 minutes produced a. substantial improvement in mud thinningproperties and gas blowing brings about a further improvement. Thisimprovement with gas blowing is relatively small and gas blowing is notessential to bringing about the main result of our invention which isthe unexpected result of the heat treatment. Furthermore, the effectdoes no appear to be due to oxidation, as might be expected with air oroxygen since the improvement over heat treatment is small and the samewhether the blowing is done with air, oxygen, nitrogen or other inertgas.

The original spent sulfite liquor and the heated, argon blown sampleswere also converted to the iron salts by dissolving in water, adding byweight of ferric sulfate (24.5% Fe) as a solution and neutralizing to pH3.5 with sodium hydroxide. The mixtures were heated to 90 C.,centrifuged to remove the precipitates of calcium sulfate and dried at60 C. These products were tested for thinning of gypsum base mud. Theresults in Table 2 of Example I show the improvement gained by the heattreatment. These products may be further improvided by oxidation withthe agents herein before described in accordance with our invention anddiscovery.

Table 1 of Example I EFFECT OF HIGH TEMPERATURE HEAT TREATMENT ON LIMEMUD THINNING [Tests at 6.0 lbs/bbl. in limed mud rolled 20 hr. at: F

Table 2 of Example I EFFECT OF HIGH Tlillllll lRA'lURE HEAT TREATMENT ONFRESH \VATER MUD TIIINNING [Tests at 4.0 lbs/lib]. in gyp mud rolled 20hr. at 150 F.)

| Sample pH i LG. IV Y 10 G W1.

lronSaltolOriginalLiquor 8.3 13.5 5.5 13.0 18.0 16.8 Iron Salt of ArgonBlown Sample 8.2 1.5 6.0 5.5 12.5 12.8

By purifying herein is meant partially or completely removing thenonlignosulfonate portions of the spent sulfite liquor as byfermentation, fractionation, lime precipitation in bulk or by smallincrements, by salting out, or by reaction with organic amines andseparation as precipitates or as non-miscible solutions; in short, byany of the methods known to the art. Particularly, purifying includesthe removal of sulfur dioxide, otherwise unnecessary consumption of theoxidizing agent occurs. Such removal may be accomplished by steamstripping and/ or air blowing and this particularly at elevatedtemperatures. Purifying may also include removal of insoluble inorganicprecipitates such as calcium sulfite and sulfate. In fractionating weinclude fractionation with aqueous organic solvents. By "separating thespent sulfite liquor solids is meant isolating in whole or in part thesaid solid components of the spent sulfite liquor by any of the methodsherein disclosed. By *concentrating" the spent sulfite liquor solids ismeant reducing the volatile content of the spent sulfite liquor in partor to the degree that there remain only the solid components of thespent sulfite liquor.

When the phrase, adding to the spent sulfite liquor solid components isused, the solids could be in the original solution or isolated by any ofthe methods herein mentioned or known to the art. When the statement isherein used treating to form a salt having an element selected from thegroup consisting of iron, aluminum, chromium, and copper, it isintended, of course, to include combinations of said elements. Likewise,in the listing of the oxidizing agents, combinations of said agentswhere chemically feasible are included. When it is directed to add to ortreat spent sulfite liquor, it is intended to employ or treat saidliquor substantially as received from the digester excepting that thetemperature of the spent sulfite liquor may be as it is received fromthe digester or after the spent sulfite liquor is cooled.

Where fermented spent sulfite liquor was used, in the examples herein itwas prepared from the ellluent from the commercial production of ethylalcohol by fermentation of spent sulfite liquor with bakers yeast(Sac-charomyces cercvz'sine). In the fermentation process the spentsulfite liquor as it is received from the blowpit is stripped(distilled) with steam to remove sulfur dioxide, cooled to about 30 C.and neutralized to about pH 4.5 with lime. Bakers yeast is then added tothe neutralized spent sulfite liquor to ferment the hexose sugarspresent to alcohol. The fermentation lowers the reducing value of thespent sulfite liquor as measured by Fehlings solution from about 24percent to about 10 percent expressed as glucose and based on the spentsulfite liquor solids. Yeast is recovered for reuse by centrifuging andthe alcohol is removed from the fermented liquor by stripping withsteam. The resultant liquor is the fermented spent sulfite liquor. Thismethod of fermentation is disclosed more fully in United States LetterPatent No. 2,430,355 granted to Joseph L. McCarthy on November 4, 1947.Any method of fermentation which primarily utilized the carbohydratesmay be used. The fermentation may be either anaerobic or aerobic by anyof a number of microorganisms including bacteria and yeast of the Torulagenus.

In using a gypsum base mud, the calcium sulfate may be added to the mudfrom the strata being drilled.

Where examples of substances are given it is to be understood the sameis done by way of illustration and not limitation.

We claim:

1. A process for producing useful products from sulfonatedlignin-containing material comprising the step of forming a soluble saltof a sulfonated lignin-containing material which has been heat treatedat a temperature between about 170 C. and 210 C. and highertemperatures, said soluble salt containing a metal ion selected from thegroup consisting of iron, aluminum, chromium, copper and combinationsthereof.

2. The process of claim 1 wherein said sulfonated lignin containingmaterial is obtained from spent sulfite liquor.

3. A process for producing useful products from sulfonatedlignin-containing material comprising the step of forming a soluble saltof a sulfonated lignin-containing material which has been heat treatedat a temperature between about 170 C. and 210 C. and highertemperatures, said soluble salt having a cation selected from the groupconsisting of iron, aluminum, chromium, copper and combinations thereof,and oxidizing said salt with an axidizing agent having an oxidizingpower stronger than an oxidation potential of about 1.3.

4. The process of claim 3 wherein said sulfonated lignin-containingmaterial is obtained from spent sulfite liquor and wherein saidoxidizing agent is selected from the group consisting of hydrogenperoxide, ozone, lead dioxide, chromic acid, chlorine, alkali andalkaline earth metal hypochlorites, alkali metal chromate, alkali metalpermanganate, alkali metal persulfate, alkali metal perborate,electrolytic oxidation and combinations thereof.

5. The process of claim 2 wherein the metal ion is 6. The process ofclaim 2 wherein the metal ion is aluminum.

7. The process of claim 2 wherein the metal ion is chromium.

8. The process of claim 2 wherein the metal ion is copper.

9. The process of claim 4 wherein the cation is iron and the oxidizingagent is an alkali metal chromate.

10. The process of claim 4 wherein the cation is chromium and theoxidizing agent is an alkali metal chromate.

11. A process for producing soluble useful products from sulfonatedlignin-containing material comprising the step of oxidizing a sulfonatedlignin-containing material which has been heat treated at a temperaturebe- 26 tween about C. and 210 C. and higher temperatures, said materialbeing oxidized with an oxidizing agent having an oxidizing powerstronger than an oxidation potential of about 1.3.

12. The process of claim 11 wherein said sulfonated lignin-containingmaterial is obtained from spent sulfite liquor and wherein saidoxidizing agent is selected from the group consisting of hydrogenperoxide, ozone, lead dioxide, chromic acid, chlorine, alkali andalkaline earth metal hypochlorites, alkali metal chromate, alkali metalpermanganate, alkali metal persulfate, alkali metal perborate,electrolytic oxidation and combinations thereof.

13. The product of the process of claim 1.

. The product of the process of claim 4. The product of the process ofclaim 5. The product of the process of claim 6. The product of theprocess of claim 7. The product of the process of claim 8.

. The product of the process of claim 9. The product of the process ofclaim 11.

21. A process for producing useful products from spent sulfite liquorcomprising the steps of heat treating spent sulfite liquor at atemperature between about 170 C. and 210 C., and interacting said spentsulfite liquor with a soluble metal ion selected from the groupconsisting of iron, aluminum, chromium, copper and mixtures thereof,said metal ion being present in an amount chemically equivalent to l50%of the sulfate salt thereof, based on the weight of the spent sulfiteliquor solids.

22. A process for producing useful products from sulfonatedlignin-containing material comprising the step of forming a solublecomplex salt of a sulfonated lignincontaining material which has beenheat treated at a temperature between about 170 C. and 210 C., saidcomplex salt containing a cation selected from the group consisting ofiron, aluminum, chromium, copper and mixtures thereof.

23. A process for producing useful products from sulfonatedlignin-containing material comprising the steps of heat treating saidmaterial at a temperature between about 170 C. and 210 C., andcomplexing said material with a metal selected from the group consistingof iron, aluminum, chromium, copper and mixtures thereof, to produce asoluble product, said metal being present in an amount chemicallyequivalent to 1-50% of the sulfate salt thereof, based on the weight ofthe sulfonated lignin in said material.

24. The process of claim 5 wherein the iron is present in an amountchemically equivalent to l-50% of the sulfate salt thereof, based on theweight of the spent sulfite liquor solids.

25. The product of the process of claim 10.

References Cited in the file of this patent UNITED STATES PATENTS2,401,373 Robinson et al. June 4, 1946 2,491,436 Barnes Dec. 13, 19492,822,358 Hearon et a1 Feb. 4, 1958 2,935,473 King et al. May 3, 19602,935,504 King et a1 May 3, 1960

3. A PROCESS FOR PRODUCING USEFUL PRODUCTS FROM SULFONATEDLIGNIN-CONTAINING MATERIAL COMPRISING THE STEP OF FORMING A SOLUBLE SALTOF A SULFONATED LIGNIN-CONTAINING MATERIAL WHICH HAS BEEN HEAT TREATEDAT A TEMPERATURE BETWEEN ABOUT 170*C. AND 210*C. AND HIGHERTEMPERATURES, SAID SOLUBE SALT HAVING A CATION SELECTED FROM THE GROUPCONSISTING OF IRON, ALUMINUM, CHROMIUM, COPPER AND COMBINATIONS THEREOF,AND OXIDIZING SAID SALT WITH AN AXIDIZING AGENT HAVING AN OXIDIZINGPOWER STRONGER THAN AN OXIDATION POTENTIAL OF ABOUT -1.3.